FIG. 9 shows an electronic device having an integrated connector. In this device, the first end of each connector pin 500 is soldered to a printed circuit board (PCB) 100. The second end is fixed to a case 200 by insert molding and its tip is exposed to the outside of the case 200. Edges of the PCB 100 are sandwiched by the case 200 and a cover 300. The case 200 and the cover 300 are fixed together with mounting screws 600. Therefore, the PCB 100 is fixed between the case 200 and the cover 300.
The electronic device may be exposed to high temperatures when it is installed in an engine compartment. It may be exposed to a temperature of approximately forty degrees Celsius below zero when the vehicle is used in countries that are subject to severe climatic changes, such as Sweden and Russia. Components of the electronic device are made of different kinds of materials having different thermal expansion coefficients. For instance, the case 200 and the connector pins 500 are made of a resin and brass, respectively. When the temperature to which the electronic device is exposed varies greatly, the case 200 and the connector pins 500 expand or contract at different rates. Therefore, stresses are applied to the soldered portions of the connector pins 500 due to the different rates of expansion or contraction between the case 200 and the connector pins 500.
Moreover, the PCB 100 and the cover 300 are made of a resin and metal, respectively. The expansion or contraction rate of the PCB 100 is larger than that of the cover 300. When the PCB 100 expands or contracts, it bends and stresses are applied to the soldered portions of the connector pins 500. The soldered portions of the connector pins 500 are not highly resistant to stress. Therefore, cracks may appear in the soldered portions. If the device is used while the cracks are present, the cracks may become larger and cause electrical failures.